This invention is an apparatus for planting seedlings in soil in commercial growing fields. This type of agriculture is sometimes called field transplant production. Growing crops from seedlings has been shown to improve crop yields over conventional seeding of growing fields. The seedlings are generally produced in greenhouses in growing media contained in rectangular trays that are returned to the supplier for re-use. Generally, peat containers, clay pots, peat pellets, fiber blocks, and individual plastic pots are no longer used for mass production. Such containers were used in the past and apparatus for planting seedlings in this form are known in the art. The seedlings seeds are sown in a prepared growing medium installed in growing trays. Because of multiple usages, the trays must be properly sanitized after each use or disease problems occur. The resulting seedling root mass and growing media in the seedling cell is frequently called a root ball.
Numerous shapes, sizes and configurations of transplant container trays are available. Trays used in the United States usually have straight row arrangements of inverted pyramid-shaped cells that are open on top, taper toward the bottom and have a hole in the bottom for water passage. Some trays have rounded configurations at the bottom. They may have cell sizes as small as ½-inch square or as large as 2-inches square. The number and spacing of cells in a tray depends on the tray dimensions and cell size.
Different plant species require differing amounts of space, nutrients and water. Smaller cell sizes are desirable to maximize the number of seedlings in a given seedling growing space, which reduces cost. Certain tray cell sizes are more suitable for some plant species than others. Larger cells hold a greater volume of growing media that enables them to retain more water and nutrients. Therefore, transplants growing in larger cells require less frequent watering and fertilizing. This helps reduce the likelihood of a moisture or nutrient stress. Also, larger-celled containers normally produce stockier and earlier plants.
Different seedling suppliers will use differing sizes of seedling trays to match the support frames in the greenhouse. The result is the planter of seedlings who wishes to obtain the best price on seedlings often must deal with a variety of seedling container tray sizes and seedling cell spacing configurations.
Manual planting of seedlings grown in large trays is a labor-intensive activity. Therefore machines to reduce the labor cost have been developed and are available in the art. U.S. Pat. No. 4,616,578 (Talbott), U.S. Pat. No. 4,854,802 (DeGroot), U.S. Pat. No. 4,893,571 (Häkli et al), U.S. Pat. No. 5,209,170 (Kobayashi), U.S. Pat. No. 5,541,116 (Gao), U.S. Pat. No. 5,445,089 (Houng et al), U.S. Pat. No. 5,477,791 (Nakashima et al), U.S. Pat. No. 5,564,352, (Kondo et al), U.S. Pat. No. 5,644,999 (Williames), U.S. Pat. No. 5,676,072 (Williames), U.S. Pat. No. 5,765,491 (Brower), U.S. Pat. No. 5,868,086 (Williames), U.S. Pat. No. 6,327,986 (Williames) and U.S. Pat. No. 6,591,766 (Williames) describe numerous planting machines that require uniform, or special tray sizes and/or cell configurations, or major modifications to the apparatus in order to use a different tray size or configuration. Another fixed tray size planter is described in this inventor's U.S. Pat. No. 4,454,829. What is needed is a seedling planter that is field-adjustable to accommodate different seedling tray sizes and configurations.